Manufacture of filaments for incandescent lamps



M'IINITE STATES PATENT OFFICE.

THOMAS A. EDISON, OF MENLO PARK, NEW JERSEY.

MANUFACTURE OF FlLAMENTS FOR INCANDESCENT LAMPS.

SPECIFICATION forming part of Letters Patent No. 470,922, dated March15, 1892.

Application filed October 10, 1883. Serial No. 108,563. (No specimens.)

To all whom it may concern:

Be it known that I, THOMAS A. EDISON, o Menlo Park, in the county ofMiddlesex and State of New Jersey, have invented a new and usefulImprovement in the Manufacture of Incandescing Conductors for ElectricLamps, (Case No. 594,) of which the following is a specification.

The object of this invention is to produce incandescing conductors forelectric lamps which shall be of even density and resistance. Heretoforein manufacturing such conductors from paper they have been cut orpunched from single sheets of paper of the proper thickness, or havebeen built up by placing together several filaments separately out frompaper sheets with the fiber in some of the filaments at an angle withthose in other filaments, and which have been compressed and carbonized.In the former case any defects in the texture of the paper or slightvariations in the thickness of the sheet will appear in the conductors,causing differences in the density and resistance of such conductors asmay, be cut from portions of the sheet containing the defects orvariations. In the latter case the article is improved; but the processof making it is slow and difficult. Iremedy the objections mentioned byemploying two or more sheets of thin paper placed one upon the other andformed by a carbonizable cementing material into a homogeneous sheet.From this sheet the filaments are cut or punched, as before, and arethen carbonized, or the entire sheet may be-carbonized and theconductors formed from it after carbonization. By thus placing severalsheets together the defects in any one sheet are counteracted orcompensated for by the other sheets, each defective portion extendingthrough only a part of the entire sheet, from which the filaments arecut.

In placing the sheets together I prefer to place them so that the grainof the paper of each sheet lies at right angles to that of the adjacentsheet or sheets. Filaments cut from a single sheet are weakened from thegrain of the paper lying all in one direction, and this defect isobviated by placing the two or more sheets together in the mannerstated.

The cementing material used to unite the tissue-paper sheets may begum-tragacanth or any other suitable carbohydrate or viscous substancecarbonizable without entire volatilization. The sheets of tissue-paper(which I prefer to use) are preferably soaked in a thick mass of thissubstance, or the latter may be rubbed upon the surfaces of the sheets.Two or more of these sheets are then placed together, preferably withthe grain at right angles, as explained. The sheet thus formed is driedunder strain or pressure, or both, so that in drying it will contractevenly and produce a sheet or blank of even texture and thicknessthroughout. From this blank the conductors are formed in the desiredshape and are then carbonized in a suitable manner, orthe filaments may,as stated, be formed after carbonization.

Instead of covering the sheets with a cementing material, such materialmay be formed upon the sheets by treating them separately with thehydrofluoric acid to gelatinize the surfaces of the sheets. The sheetsare then placed together and dried under strain and pressure, as before.

What I claim is 1. The method of forming blanks or sheets for thepurpose mentioned, consisting in treating separately two or more sheetsof paper with hydrofluoric acid to form a cementing material and thenplacing such sheets together, substantially as set forth.

2. The method of forming carbon filaments for incandescent lamps, whichconsists in treating two or more sheets of paper with hydrofluoric acidto form a cementing material,

placing said sheets together to form a single sheet, 'and cuttingfilaments therefrom, substantially as described.

3. The method of forming carbon filaments for incandescent lamps, whichconsists in treating two or more sheets of paper with hydrofluoric acidto form a cementing material, placing said sheets together to form asingle sheet, and cutting filaments therefrom, substantially asdescribed.

4. The method of forming carbon filaments for incandescent lamps, whichconsists in This specification signed and witnessed this treating two ormore sheets of paper with hy- 14th day of September, 1883. (lrofluoricacid to form a cementing material, placing said sheets together to forma single TIIOS. A. EDISON. 5 sheet, the grain in one sheet being at anangle with the grain in the other sheet 01 sheets, Vitnesses: andcutting fi'lam ents therefrom, substantially H. WV. SEELY, as described.EDW'ARD II. PYAT'I.

